The identification and tracking of animals and/or carcasses prior to and throughout being processed at an abattoir, saleyard or movement is extremely important. A principal purpose of electronically identifying animals is to individually identify animals or carcasses in a lot or run as well as the need to have a direct link to a national database for checking residue status as well as recording movements and a whole of life history of individual animals. This can be achieved as each animal or carcass passes an antenna designed to read EID carried by the animals or carcasses. If an animal or carcass does not carry an EID or its EID is not functioning, and is thus not able to be read by the antenna then that animal or carcass will be included in the lot or run and will be counted in error. The inclusion of animals or carcasses which are unable to be accounted for, can have disastrous consequences where animals or carcasses that have been electronically identified and are known to be disease free are inadvertently mixed with diseased animals or carcasses that have non-functioning EID and have been included in the lot or run. This has become especially important with the outbreaks of bovine spongiform encephalitis (BSE) and foot and mouth disease in the United Kingdom, Europe and South America. In order to protect the animals or carcasses in countries, which are not as yet affected by these or other diseases, various methods of identifying and tracking animals or carcasses have been developed. Among the more effective tracking and identification systems is the use of electronic ear tags or rumen pellets, which are ingested by a ruminant animal, or the use of other electronic identification devices. Prior art have been described in Patent Nos. WO 97/46083 and WO 93/22907 in the case of tags and PCT/AU95/00218 in the case of pellets.